I already did answer you on Discord but to clarify, i think both products do the same when we are talking about use USB controllers and JAMMA/NEOGEO, but with different features.
I'm happy that you liked it!
Pademic times were terrible for people like us who work with electronics; we had to wait nearly a year to get the main IC for USB2DB15, but things will be different in 2023!
Thank you for your support!
It's nice to see that people here love @RGB HAS!
Some times when NEO-C1 is bad you will get issues on graphics. So try to replace it first.
If still persist, ZMC2 may be the culprit or bad traces around it.
But then it would be a PSU problem, since there is nothing in the way of the 12V line to the amplifier. Also, this problem would happen with all JAMMA boards, not just this specific one.